Sampling

Sampling is usually discussed in terms of data collection. It refers to which members of a population to collect data from, or how to select data form some canon (e.g. if analysing examination questions from an archive of examination papers going back decades, offering too many for close consideration of each question).

Sampling may also be considered at the data analysis stage if data collection has produced too much data to analyse within the resources of a project, or some data is clear redundant.

Ethical considerations suggest we should not deliberately collect data that will not be analysed, but when we are unsure how much data may be generated we may have to err on the side if caution. We may need to plan for possible drop-out of participants that does not in the even occur, for example. We may be selecting a case for case study depending upon the quality of data available from different participants or institutions.

Two approaches to sampling

"There are two general strategies or logics for selecting units (organizations, events, people, documents, locations, etc.) to study in qualitative work: an empirical or statistical strategy and a theoretical or purposive strategy.…

In the logic of sampling based on an empirical or statistical strategy, sample units are chosen based on their representativeness of some wider population of units. …

In the logic of sampling based on a theoretical or purposive strategy, units are chosen … for their relevance to the research questions, analytical framework, and explanation or account being developed in the research” (Schwandt, 2001: 232).

Schwandt, T. A. (2001). Dictionary of Qualitative Inquiry (2nd ed.). Thousand Oaks, California: Sage Publications.

The sampling approach must be coherent with the rest of the research design

In confirmatory research, using statistical approaches it may be important fro results to be valid that sampling has a random element so that all members of some population have the same chance of being included in the sample. (See: Taber, K. S. (2019). Experimental research into teaching innovations: responding to methodological and ethical challenges. Studies in Science Education. doi:10.1080/03057267.2019.1658058)

In discovery modes of research theoretical grounds may be used to select the sample which offers the most information in relation to our research questions. For example, in grounded theory methodology, a general iterative strategy of ‘theoretical sampling’ is used during the research.

Index of topics